1. Field of the Invention
The invention relates to hollow bodies with at least two oval sleeves and an annular connecting journal arranged between each of the sleeves, and more particularly, to cam groups formed from part of the outer peripheral surface of the sleeves having annular connecting journals been each sleeve. A projects beyond the connecting journals at least in the region of the sleeve having a smaller radius. The projection is greater at the crown of the smaller radius than in the other regions, and the circumference of the annular connecting journal is smaller than the inner circumference of the oval sleeves. The invention also relates to a process to for producing such hollow bodies.
An example of such hollow bodies, in reference to which the invention is described but to which the invention is not limited, are arrangements of at least two cams, known as cam packs or cam groups. In the case of joined hollow cam shafts, it is known to combine at least two cams into groups, whereby the individual cams of the group are connected to one another by means of connecting sleeves.
2. Description of the Prior Art
Cam groups of this type are known in the art, as disclosed in European Patent Number EP 0 213 529, wherein the cams and the connecting sleeves arranged between them have the same inner diameter. When such cam groups are joined to a tube, the tube sections located below the cam groups are deformed plastically, but the tube groups are only deformed elastically. The resilience of the cam groups requires the use of very high pressure to produce the pressure responsible for the frictional connection between the cam groups and tube sections.
In order to avoid these high pressures, cam groups are suggested in European Patent Number EP 0 309 899, wherein the cams have larger inner diameters than the connecting sleeves, so that when expansion takes place, only the connecting sleeves are held frictionally. As a result, especially if the connecting sleeves are thin-walled, significantly reduced deformation forces are required.
German Patent Number DE A 2232438 describes a hollow body that consists of a hollow cylindrical tube, which is broadened in a die around the area of the cams while maintaining its circular-cylindrical shape in the area between the cams. The hollow body described in DE A 2232438 is produced by die casting where the material of the original hollow cross-section flows into recesses in the die and whereby the material of the tube can also flow, along with the cams, into the cam recesses of the die. The resulting finished hollow cam tube has no significant differences in wall thickness over its entire length. DE A 2232438 does not describe a hollow body that has equally large cross-sectional areas in the sleeves and connecting journals. Furthermore, the material between the sleeves and connecting journals is not sheared off. Finally, no tube produced according to the description of DE A 2232438 is shaped over its entire length into an oval, which shape corresponds to the shape of the finished sleeves.
German Patent Number DE A 3439973 describes a process wherein a hollow body is produced from a tube which is circumferentially more narrow in the area of connecting journals and which circumferentially broadens to the shape of sleeves in the cam areas. According to this process, the tube is thus not shaped over its entire length into an oval shape corresponding to the shape of the sleeves. Furthermore, excess material is not sheered off between the sleeves and the connecting journals. Accordingly, hollow bodies produced according to the process disclosed in DE A 3439973 are broadened only in the cam area, not over the entire length of the hollow body, as in the present invention.
Known cam packs of this type are usually cast or sintered or produced from a solid shape.
The manufacture of such cam groups is very expensive.